Author

Johnson, Ruth M.

Date

2008

Advisor

Dannemiller, James L.

Degree

Doctor of Philosophy

Abstract

Most research studies on crossmodal processing of visual and tactile modalities have found that vision enhances touch. Nevertheless, it is unclear whether vision increases tactile sensitivity or changes participants' response criteria for reporting touch. The following set of studies demonstrated that some experimental manipulations can lead to a small increase in tactile sensitivity; however, all experiments showed a consistently strong response bias to report feeling a touch with a concomitant visual stimulus. Further experiments sequenced the temporal processes associated with the visuotactile response bias and determined that greater visual influences on electrotactile processing occurred at smaller crossmodal asynchronies. A final experiment demonstrated that the reported electrotactile enhancement bias on light-present trials can be increased with transcranial magnetic stimulation (TMS) over the posterior parietal cortex 200 ms after visual and electrotactile stimuli presentation. Further research needs to be conducted to determine more precise cortical locations and temporal sequences of the crossmodal interactions between vision and touch.